Mechanical Behavior Analysis Of Composites Honeycomb Sandwich Structure

With the development of composites in recent years,composites honeycomb sandwich structure is now gradually replacing the traditional metal honeycomb sandwich structure,and are more and more used in aerospace structures.Due to the complexity of the internal structure and failure mechanism of composites,it's far more difficult to analyze the mechanical behavior of composites honeycomb sandwich structure than traditional metal honeycomb sandwich structure.Therefore,it's of great academic significance and engineering value to develop an analysis method of composites honeycomb sandwich structure.In this paper,the equivalent modeling method and static strength analysis method of composites honeycomb sandwich structures have been studied,the main research work is as follows:(1)The modeling methods of equivalent model and fine model for static strength analysis of honeycomb sandwich structure are studied.The panel of equivalent model and the panel of fine model for static strength analysis of honeycomb sandwich structure are modeled by using solid element,which unifies the modeling method of the panel in the two models.So,it is convenient to use these two models in further analysis of the mechanical behavior of composites honeycomb sandwich structure.For the fine model,the cohesive layer is used to simulate the mechanical behavior of the adhesive layer.The research shows that the equivalent model based on solid element can accurately characterize the linear mechanical properties of honeycomb sandwich structure;Compared with the fine model that panel is modeled by shell element,the fine model that panel is modeled by solid element can characterize the failure mode of honeycomb sandwich structure while accurately calculate the yield load;Because the cohesive layer is used to simulate the mechanical behavior of the adhesive layer,the honeycomb sandwich structure fine model can accurately characterize the delamination failure mode caused by the debonding of adhesive layer.(2)The multiscale progressive damage failure analysis of 2D braided SiC/SiC composites is carried out,which provides a basis for the subsequent application of this method to analyze the mechanical properties of the panel of composites honeycomb sandwich structure.The microscale interphase is considered in the multiscale analysis process across macro-meso-micro scale,so that the failure behaviors such as interphase debonding and fiber bundle pull-out can be approximately characterized.The condensated amplification factor is used to transfer multiscale information,combining the mesoscale and microscale failure theory and the calculation method of equivalent elastic parameters of braided composites,the multiscale progressive damage failure analysis of 2D braided SiC/SiC composites across macro-meso-micro scale is carried out.The research shows that the numerical simulation can accurately calculate the strength limit of 2D braided SiC/SiC composites;The microscale interphase can not be ignored,if the microscale interphase is ignored,the material properties will be greatly enhanced;This method can simulate the damage and failure process of materials at macro-meso-micro scale.(3)The equivalent modeling method and static strength analysis method of SiC/SiC composites honeycomb sandwich structure are studied.Based on the hierarchical multiscale analysis method,considering the random distribution characteristics of microscale fibers and matrix pores at mesoscale and microscale,the mesoscale and microsclae representative volume element models which are closer to the actual structure are established,and the equivalent elastic parameters of SiC/SiC composites are calculated by using the prediction method of equivalent elastic parameters based on strain energy.Thus,the method of obtaining the equivalent elastic parameters of the panel in the equivalent model of SiC/SiC composites honeycomb sandwich structure is improved.The multiscale analysis method of 2D braided SiC/SiC composites is applied to the panel of SiC/SiC composites honeycomb sandwich,then a static strength analysis method of SiC/SiC composites honeycomb sandwich structure is developed.The lightweight degree of SiC/SiC composites honeycomb sandwich structure compared with traditional metal honeycomb sandwich structure is quantitatively evaluated by using specific strength as the basis for comparison.